Explosion as a phase transition due to the change of the gradient symmetry of the distortion tensor.

It is shown that the destruction of a continuous elastic medium is a phase transition associated with a change in the gradient symmetry of the equations of state for the distortion tensor. The equations of state for the distortion tensor, as a compensating field of the minimal fundamental interaction, are derived from the action minimum. In a continuous elastic medium, the distortion tensor is proportional to the conjugate stress tensor. The continuous medium is destroyed at critical stresses or pressures. At the same time, the vortex tension of the distortion tensor penetrates into it and the elasticity disappears. As a result of this phase transition, linear defects and cracks are formed in solids state, and high-temperature plasma occurs in the gas and an explosion occurs. It is shown that the explosion and lightning are the same phase transition, which is caused by the occurrence of a critical vortex tension of the distortion tensor.

A Fiber Optic Conjugate-Stress Sensor for Prognostic Health Monitoring of Fatigue

A fiber optic conjugate stress sensor (FOCSS) is explored for monitoring fatigue in aluminum cantilever beams. It is known that as damage accumulates due to fatigue, microstructural changes result in an altered modulus; so in this work, fatigue is continuously monitored by measuring the evolution of the effective modulus of the host. Conjugate stress sensing extracts host modulus from two extensometers of different stiffnesses (termed the stiff and compliant sensors) by using a known transfer function from sensor strains to host modulus. The sensing concept is explained and the transfer function is determined from a lumped-mass spring model. Finite element modeling is carried out, which reveals the host modulus assessed by the FOCSS is more sensitive to fatigue damage of a structure than its natural frequency (another commonly used macroscale measure of fatigue). The FOCSS capabilities are next verified in aluminum beam fatigue experiments. The FOCSS estimated modulus is seen to decrease with accumulation of fatigue damage. However, fatigue of the glue used to attach the sensors to the specimen is found to obscure the sensor’s response to host fatigue, thus presenting an important source of experimental error. Future work aims to deconvolve FOCSS sensitivity to glue fatigue from the response to host fatigue. Our finite element simulation results indicate that the FOCSS can significantly hasten early warning and extend the prognostic horizon, which can greatly reduce logistical burden and increase consumer confidence.